Diagnostics of metal structures made of ferro- and paramagnetic materials by the coercive force method

The coercimetry based on the Hall effect as a source of primary information is the main method of magnetic control (when classified according to the primary informative parameter) in technical inspection of potentially dangerous metal structures. Coercive force (considered as the intensity of an external magnetic field applied to a ferromagnet magnetized to saturation for complete demagnetization of the latter) is the most structure-sensitive characteristic which provides for rapid diagnostics of the material in production conditions. A linear character of change in coercive force upon application of cyclically varying stresses provides the possibility of reliable determination of the residual life of the structure. We propose a method for determining the residual life of structures made of non-ferromagnetic materials exposed to cycle mechanical loads proceeding from data on changes in the coercive force of steel witness samples (samples made of ferromagnetic material, working together with the structure under study made of non-ferromagnetic material). It is shown that the rate of change of the coercive force in the ferromagnetic witness sample correlate with the stresses in the nonferromagnetic structure. This makes it possible to determine directly the residual life of a non-ferromagnetic structure, which significantly increases the accuracy of estimating the residual life of potentially hazardous structures made of non-ferromagnetic materials. The results obtained can be used to determine the technical condition (based on the level of accumulated damage) of such structures as, for example, pedestrian bridges made of aluminum alloys.